Electromagnetically induced intrinsic bistability at the atomic level

Theory predicts that intrinsic bistability can be observed with two interacting systems, provided that some general conditions on correlation time of the interaction and induced line shifts are fulfilled. Two compounds with strongly interacting systems have been investigated in order to reach these conditions: Yb3+:YCa4O(BO3)3 (rare earth-rare earth ion interaction) and Nd3+:GdFe3(BO3)3 (rare earth-transition metal ion interaction). Although Yb3+ cooperative luminescence bistability has been observed in the first case, the effect of Yb3+-Yb3+ interactions on the observed processes could not be demonstrated. In the second case, a transmission switch is observed as a function of the laser power, but without a defined hysteresis. This is attributed to small excited populations for both Nd3+ and Fe3+ ions.